Electric flash welding machine



Oct. 6, 1942. s, H. GORDON ETAL 2,298,051

ELECTRIC FLASH WELDING MACHINE Filed Jan. 18, 1941 5 Sheets-Sheet 1 Fig I.

Oct. 6, 1942. H- GORDON ETAL 2,298,051

ELECTRIOFLASH WELDING momma Filed Jan. 18, 1941 5 Sheets-Sheet? Fig. 2.

Oct. 6, 1942.

s. H. GORDON ETAL ELECTRIC FLASH WELDING MACHINE Filed Jan. 18, 1941 5 Sheets-Sheet 3 WVVE/VRMS 5.H.GOR DON NF. YOUNG ATTORNEYS Oqt. 5, 1942. s. H. GORDON ETAL 2,293,051

ELECTRIC FLASH WELDING'MAGHINE FilOd Jan. 18, 1941 5 Sheets-Sheet 4 Fig.4.

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flair) diltu w A TTORNEKS Patented Oct. 6, 1942 ELECTRIC FLASH WELDING momm:

Samuel Hunter Gordon and William Forbes Young, Inverness, Scotland Application January 18, 1941, Serial No. 375,074 In Great Britain January 11, 1940 I 6 Claims. 'Ihisv invention relates to automatic electric flash-w elding machines of the kind described in 7 Patent No. 2,187,452. In the specification of that patent means are described whereby a reciprocating motion of approach of one of the workpiecesto'bewelded-to the other, for the purpose of preheating the workpieces, is maintained by v fluctuations of fluid pressure in a fluid-operated feed mechanism, these fluctuations being brought about by the meeting together of the cold unsoftened workpieces. In the embodiment I of that invention described in the priorspecification the regulation of the speed of the feeding movement was efifected by means of an adjustable creep valve, whereby the rate at which liquid flowed into or out of a hydraulic cylinder could be adjusted. In some circumstancesthis mode of regulating the feed movement has the disadvantage that with a given adjustment the speed will vary with the temperature of the liquid. It is the object of the present invention to provide an improved feed mechanism which among other advantages would be free from liability to undesired variation due to changes of temperature. According to this invention the moving head by-a mechanically driven reversible pump, the reversing means being under the control of a (Cl. Gil-54.5)

not dependent upon the temperature of the liquid.

Referring to the accompanying drawings:

,! Figure l is a diagrammatic side elevation partly in section of mechanism according to this invention.

Figure 2 is a side elevation partly in section of the pump mechanism,

Figure 3 is a plan of Figure 2, and

10 Figure 4 is a circuit diagram,

Referring to Figure 1, the feed mechanism consists of two hydraulic cylinders Ill, l2 placed back to back and secured to a fixed part ll of the welding machine. The cylinder I0 is larger in diameter than the cylinder 12 and a ram I6 in the cylinder i0 is connected directly to the moving head l6, so that outward movement of the ram i6 causes the forward feed movement. A ram in the cylinder I2 is attached to a crosshead [8, the outward movement of the ram 26 thereby causing the return motion of the moving head.

The pump consists of a double ram compris- 425 ing a fixed cylinder 26, a ram 28 moving in this of the welding machine is moved in both direc- 'tions'by hydraulic means supplied with liquid cylinder and bored to receive a fixed ram 30. The cylinder 26 is connected by a pipe 32 to the feed cylinder l0 and the bore in the moving ram 28 is connected by a pipe 34 to the return cylindevice sensitive to the pressure of the liquid der through a passa e 36 extendin from end which causes the forward movement of the moving head.

It will be appreciated that when the cold workpiecesmeet they will oppose resistance to the feed movement, thereby causing a rise of pressure in the hydraulic driving means and when this pressure exceeds a predetermined aniount the movement of the pump is reversed automatically thereby separating the workpieces. The pressure thereupon falls, the pressure-sensitive deviee is no longer operative and the pump reverts ture that flashing occurs, whereupon no further mechanical resistance to the feed movement occurs, the pressure of the liquid does not rise beyond the predetermined limit and therefore the forward feed movement continues uninterrupted- Owing to the fact that the pump is mechanically driven and that restricted orifices are not to end of the fixed ram 36. The ratio of the diameters of the pump cylinder 26 and of the ,bore in the moving ram 28 is equal to the ratio of the diameters of the cylinders ill, l2. Thus, if

the moving ram 28 is moved to the left liquid will be forced into the cylinder i0 thereby driving the moving head i8 forward, while liquid will be driven out of the cylinder l2 into the bore in v l the moving ram 28. If this ram 28 is moved to' 40 the right, liquid will be forced into the cylinder i2, while the liquid displaced from the cylinder ill will pass into the pump cylinder 26. The diameter of the pump cylinder is only a fraction. v of that of the forward feed cylinder i0 and there- 4 fore the travel of the moving head I6 will be much smaller than the travel of the pump ram 28. As shown in Figures, 2 and 3, the: ram 28 carries a crossh'ead 38 in which are fixed two nuts 40, 42 threaded onto similarly threaded screw spindles 46, All, Thesespindles are mounted in hearings in brackets 46, 66 which support 1 the cylinder 26 and the fixed ram 36. The spindles carry equal gearwheels 52, 64 meshing with a pinion 6.6 fixed to a shaft 68 which carries employed, the speed of the feed movement is a pulley driven by a belt 62 from an electric 20 head 22 connected by tie-rods 24 to the moving closing switch I06 coil 66 again as previously described. This cycle operations is repeated until the work pieces no longer oppose mechanical resistance at the time the pressure switch circuit is established. In these circumstances the pressure switch 72 remains closed and the pressure switch circuit is maintained, with the result that the motor continues to rotate forwards.

On the crosshead 22 is mounted an adjustable cam Ii5. At a predetermined point in the forward feed movement this cam will push down wards a pivoted lever I I6 thereby opening a valve I I8 which allows high pressure oil from an independent source to enter the forward feed cylinder l and thus drive the moving head I8 forward at an increased speed to butt the work pieces together and complete the weld. At the same time another valve I20 is opened to connect the return cylinder I2 to an oil reservoir I22 to allow the oil displaced by the rapid forward movement of the moving head to escape.

The downward movement of the lever IIGalso opens the switch I26 previously referred closes another switch I24. The opening of I26 de-energises the winding 84, thereby opening switches 26 and 86. thereby cut' off from winding 68 and the The welding current is the primary transformer winding I04 is tie-energised, and opening switch I06. When the switch I24 is closed there is a circuit from A through a, b, c, 80, I24, k, IN, ,1, e, 90, 62, 04,12, C. The switch I24 is, therefore a shunt across the pressure switch I2 and keeps the, moipr nmning forwards in spite of I2 being opened by the high pressure supplied to the cylinder I0 through the valve H0. The oil displaced from is cylinder 26 during this movement escapes through a relief valve I26 into the reservoir l22.

presently opens the forward limit switch 62 previouel referred to, which will de-energise and cause the forward motor contacts? 86 to open. This establishes a circuit A, a, b, c, II4 F, I00, 1, m, II2, C. This causes the motor to reverse momentarily and then stop.

The weld is now complete and the welded woris pieces are removed from the machine. crating handle is moved back to its original position and the lever H6 is lifted. This comes about owing to the fact that its pivots are ec- The op- The cross-head 30 carries a projection I30 which centrically mounted on the spindle I32 of the opcrating handle 16. Thus, the raising of the handle 76 depresses the right hand end of the lever I I 6 thereby causing its operative left hand end to be raised by a spring,.not shown. The valves II 0 and I20 are thereby closed, the switches 76, 00, I24 are opened, and the switches Ill, I26 are closed. The closing of 02 energises the reverse contactor coil II 2, th circuit being from A through a, b, c, 82, I44, m, II2, C. The motor runs in reverse, the pump ram 28 being moved to the right. A limit stop I36 is provided which arrests the rams I6, 20 at a predetermined posi tion. When this takes place, the pump ram 26 is still moving to the right, displacing oil past a second relief valve I36 into the oil reservoir i212. At the same time the pump cylinder :26 receives oil from the reservoir through a non-return valve I30. A second nomreturn valve serves in. the same way for the bore in the pump ram nd the two valves 38 and Mil enable the oil circuit to be filled in the first place and maintain it full against any small leakages that might take place.

A second projection. M2 on the crossh 38 ultimately opens a back limit switch its de energises the reverse contactor coil and closes the interlock switch as". The switch 86 being open, 90 cannot be energised through the forward feed circuit, but the motor-operated contacts IHB are now closed and there is a circuit from A through a, b, 0, H413, f, e, 90, 92, 94, h, C. The forward contactor 98 closes, the motor starts in the forward direction, 1 14B opens immediately thereby de-energising the coil 90, which cannot be re-energised through the forward feed circuit because is open. This brings the operation to an end and no current can flow in any of the circuits until the switch 80 is closed by the handle 16 to initiate the next welding operation.

We claim:

1. A hydraulic system comprising in combi nation hydraulic ram means operable in a forward direction and in the reverse direction, a mechanically driven reversible pump for supplying liquid under pressure to said hydraulic means, reversing means for said pump and a device sensitive to variation in the liquid pressure causing the forward movement for actuating the reversng means to cause reverse movement as a consequence of rise of liquid pressure above a predetermined limit and for again actuating said reversing means to cause forward movement as a consequence of fall of liquid pressure below said limit.

2. A hydraulic system according to claim 1, in- I said motor and which operates to reverse the direction of rotation of the motor in response to the rise or fall in pressure of the liquid as More said.

3. A hydraulic system according to claim 1, ineludin an electric motor to drive said pump and wherein said reversing mechanism includes a reversing switch, a pressure actuated switch, and an electromagnet which is energized upon closing of the pressure switch to operate the reversing switch to a, position in which it operates to reverse the direction of rotation of the motor in response to the rise in pressure of the liquid aforesaid and to return the reversing switch to its normal position in response to fall in pressure of the liquid.

i. A hydraulic system comprising in combination hydraulic rain means operable in a forward direction and in the reverse direction, said means consisting of two cylinders placed back to back, one for forward movement and the other for re verse movement, a cross head and tie rods con- 'i" the rams, a mechanically driven reversihle pump supplying liquid under pressure to said cylinders, reversing means for said pump and a device sensitive to variation in the liquid pressure causing the forward movement for actuating the reversing means to cause reverse movement as a consequence of rise of liquid pressure above a predetermined limit and for again actuating said re versing means to cause forward movement as a consequence of fall of liquid pressure below said mint.

5. A hydraulic system according to claim 4,

. wherein said pump consists of a fixed cylinder, a mechanically driven ram moved within the cylintier and bored to constitute a second cylinder, and a, fixed ram within the second cylinder, the first pump cylinder being connected to the forsecond pump cylinder being connected to the reverse cylinder of the hycylinder. and the second pump cylinder being condraullc ram means.

6. A hydraulic syst wherein the pump consistspt mechanically driven ram moved within der and bored to constitute a second cyli nd cylinder,

ted to the forward 7 WILLIAM FORBES YOUNG.

a fixed ram within the seco pump cylinder being connec nected to the reverse cylinder of the hydraulic em according to claim 4, ram means, and whereinvthe movable ram is a fixed cylinder, a driven by two nuts, carried one on either side the cylin- 6 thereof, and engaging two screw spindles posinder, and. tively geared together and mechanically rotated the first SAMUEL HUNTER GORDON. 

